1. Field of the Invention
The present invention relates generally to an apparatus for feeding sheets of paper or other types of recording media one after another from a paper stacker to a printer, such that an uppermost one of a stack of media is delivered by a feed roll or rolls in contact with the uppermost media of the stack. More particularly, the invention is concerned with techniques for easy handling of jamming troubles of the recording media in such a feeding apparatus wherein the uppermost media of the stack is delivered through a clearance between a presser member and an elastic member of the paper stacker.
2. Discussion of the Prior Art
A commonly known type of the feeding apparatus indicated above includes (a) a presser member engageable with a leading portion of the upper surface of an uppermost sheet of a stack of cut sheets placed on a sheet support member, to thereby press the uppermost sheet toward the sheet support member, (b) an elastic member disposed adjacent to the presser member for engagement with leading edges of the cut sheets, and elastically deformable in a sheet feeding direction toward a printer, according to a force of contact between the elastic member and the leading edges of the sheets, and (c) a feed roll engageable with the upper surface of the uppermost sheet, at a position rearwardly of the presser member, for exerting an advancing force on the uppermost sheet and thereby delivering the uppermost sheet toward the printer, through a clearance formed between the elastic member and the presser member due to elastic deformation or deflection of the elastic member.
In a feeding apparatus of such a type as indicated above, the cut sheets may be delivered in two different manners, depending upon the stiffness of the cut sheets to be delivered. Described more specifically, where the sheets are comparatively stiff, the sheets are delivered while being passed through the clearance between the presser and elastic members, which is formed due to elastic deformation of the elastic member by the abutting contact of the leading edges of the sheets with the elastic member, as indicated above. Where the sheets are comparatively soft, on the other hand, the uppermost sheet of the sheet stack is upwardly curved at a portion thereof between the feed roll and the presser member, and the leading end portion of the uppermost sheet abutting on the elastic member leaps over the presser member due to a resilient force created by the upward curving of the sheet, whereby the uppermost sheet clears the presser and elastic members.
In the known feeding apparatus discussed above, the presser member and the elastic member are disposed such that there exists a predetermined small amount of nominal gap or clearance between the two members in the direction of thickness of the sheet to be delivered from the sheet support member. In this arrangement, the sheets may be jammed while being delivered through the above-indicated clearance, for some reason or other, for example, due to passage of the two or more sheets through the clearance at one time, due to deviation of the sheet off the nominal path that includes the clearance. In this event, there arises a need of pulling the jammed sheet or sheets backward in the direction opposite to the sheet feeding direction, through the clearance between the presser and elastic members. Consequently, the elastic member is elastically deformed or deflected in the backward direction, i.e., in the direction opposite to the direction in which the elastic member is normally deformed during a normal sheet feeding operation. As a result, the sheet may be heavily pinched between the presser and elastic members, and may be torn or otherwise damaged. Thus, the jammed sheet may not be suitably removed from the feeding apparatus, and the removed sheet cannot be reused. Further, the elastic member may undergo an excessive amount of elastic deformation beyond its elasticity limit, causing unfavorable permanent plastic deformation, which prevents the elastic member from normally functioning to deliver the sheets.
A known feeding apparatus of the type indicated above may or may not include a pair of advancing rolls disposed ahead of the presser and elastic members, so that the sheet delivered through the clearance therebetween is advanced by the advancing rolls toward a printing mechanism of the printer. Where the apparatus is equipped with such a sheet advancing mechanism, the leading end portion of the sheet which is jammed between the presser and elastic members may be pinched between the advancing rolls. To remove the jammed sheet, the sheet must be pulled frontwardly in the sheet feeding direction or rearwardly in the direction opposite to the feeding direction. In either case, the sheet is subjected to a considerably large pull force, due to the contact of the jammed sheet with the advancing rolls at rest, which are connected to a suitable drive mechanism. This makes worse the situation in which the jammed sheet is removed.
Another problem is encountered in the feeding apparatus wherein the pair of advancing rolls is provided for advancing the sheets delivered by the feed roll from the stacker. That is, the positions of the advancing rolls in the direction perpendicular to the sheet feeding direction cannot be easily adjusted to the width of the sheets, since the advancing rolls are held in pressed rolling contact with each other. Further, once the paper stacker is loaded with a stack of sheets, the feed roll cannot be easily moved in the direction of width of the sheets, since the feed roll is held in pressed contact with the uppermost sheet of the stack.
Regarding the removal of a jammed sheet, it is also noted that the jammed sheet remains in contact with the feed roll. This also makes it difficult to remove the jammed sheet, since the feed roll is connected to a drive mechanism.
When the feeding apparatus operates to deliver recording media having folded portions, such as envelopes with gummed edges, the recording medium may be easily jammed during its passage through the clearance between the presser and elastic members, due to the folded portion or gummed edge which is easily caught by the edge of the presser member, particularly if the pressure member has a relatively small thickness.